The particularly dark appearance of the nave is due to the inadequate maintenance which over the years has led to a deterioration in the condition of the Sanctuary. Nonetheless, the mosaics with their gold background and silver inlaid mother-of-pearl, which at one point completely covered the walls of the church, retain their fascinating effect.
The wall decorations, from the Crusader period, are arranged in different bands and are partly covered by plaster.
The most recent survey carried out in connection with the restoration of the church has shown that the tesserae of the mosaics were positioned tilted downwards in order to enhance the beauty of the mosaic when observed from a position several meters below. In this manner a strong visual impact is received by the pilgrim upon entering the church, despite the poor state of preservation of the mosaics.
The most direct and precise evidence regarding the decoration is that provided by Father Quaresmi in his Elucidatio Terrae Sanctae (1626) which described all of the wall mosaics in great detail. At the lowest level, on the right, St. Joseph and the ancestors of Christ according to the Gospel of St. Matthew are portrayed.
Symmetrically, according to Quaresmi on the left side was a genealogical representation taken from the Gospel of Luke. On a second level, spaced between bands of acanthus leaves, are representations of the seven Ecumenical Councils (Nicaea, 325; Constantinople, 381; Ephesus, 431; Chalcedon, 451; Constantinople II, 553; Constantinople III, 680, Nicaea II, 787), the four provincial Councils (Antioch 268; Ancyra, 314; Sardica, 342; Gargres, 4th century) and the two local Synods (Carthage, 254; Laodicea, 4th century).
For each council there is a picture of a sacred edifice and, with the aid of an ornamental scroll, an explanation of the decision that was taken on that occasion. At the upper level we can see a series of representations of angels in procession, having feminine features and dressed in white tunics, headed towards the Grotto of the Nativity.
At the feet of one of these angels can be seen the signature “Basil” of the mosaic artist, who was probably of Syrian origin. At the crossing of the church (where the nave and transept intersect) one can still see today scenes taken from the canonical Gospels: to the north, the incredulity of Thomas, which appears to be the one best preserved, the Ascension and the Transfiguration; to the south, Jesus’entry into Jerusalem.
In the cupola of the principal apse, according to Quaresmi, was a representation of the Virgin and Child, and in the arch of the apse one of the Annunciation of Mary, between the prophets Abraham and David. On the walls below were scenes from the life of the Madonna, taken from the apocryphal writings.
On the counter-façade, above the entrance door, was a representation of the Tree of Jesse with Jesus and the prophets. This mosaic is now covered by white plaster.
The pilgrim John Phocas reported having seen during his voyage (c. 1177) a picture of the Byzantine emperor Constantine VII Porphyrogennetos in the church: this shows that even after the Schism of 1054, when the church was under the control of the Crusaders, close relations continued between the Eastern and Western Churches. An inscription in the principal apse makes reference to both Manuel Comnenus and Amalric of Jerusalem, so the mosaics must have been produced in the last decades of the Crusader presence in Palestine, which ended in 1187.
The works were commissioned by both the Crusader king of Jerusalem and the Byzantine emperor: an example of collaboration that is practically unique in history and one which highlights the importance that the Sanctuary must have had at that time.
The most recent studies carried out following the surveys for the restoration have raised a new question relative to the origin of the workers who produced the mosaics. The doubt relates to the previous assumption that local artists were employed to work on the decorative project, as normally was the case for reasons of practicality. The signatures of the mosaic artists, Ephraim and Basil, names that certainly are of Syrian origin, are a good indicator for determining the origin of the workers.
It is also possible to hypothesize that Greek workers and designers may have been involved, but it is clear that whoever produced these decorations knew very well the great monuments of the Holy Land, which had been decorated by artists coming from the West. For example, in the decorative band in the nave separating the representations of the Councils from the large figures of the angels above, where the windows are, is a second, narrower, decorative band containing an animal mask typical of European Romanesque art. T
hus, in the Bethlehem mosaics there are signs of the close relationship between Byzantine and Western art, which are blended together. The most recent investigations have established that, from the point of view of mosaic art, the church represents the culmination in the Crusader period of the encounter between Byzantine and Crusader art. T
he mosaics thus reflect the Ecumenical “face” the Church of the Nativity still presents today to those who visit it: a point of unity between the Eastern and Western churches.